I have a couple of Coleman camping utensils that take the small propane canisters. I have about a dozen canisters in my supplies. Currently they are in my basement. It's cool and dry down there, for the most part (it can get humid, but we have a dehumidifier running). I'm a little worried that these potentially explosive canisters are in my basement. We do not have a garage anymore (my mother moved in with us and the garage was used in the addition for MIL quarters). We have a small barn, but it gets *really* hot out there in the summertime.

I've stored those little cannisters in the garage and basement for years, but after someone on this board told the story of a fire and how the cannisters blew up and the fire department couldn't get near the house to put it out, I moved them.

I have them in the barn now, a good 200 yards from the house, and stored in an area that usually doesn't get over 100F. If they get too hot and blow up out there, at least they weren't in my house. And if my house catches on fire, God forbid, the cannisters won't be adding to the destruction.

I would NEVER store propane in my basement. One leak and you're literally lying atop a bomb.

The garage is a little better if it's well ventilated. I store all of my propane in my workshop. The little one pounders inside, the twenty pounders in a rack in an open shop bay. My shop is not at all air tight so leak risk from the little canisters is fairly minimal.

Heat won't affect the canisters unless you've got them in the direct sunlight or in the attic or something.

Check them periodically for surface rust in the threaded portion of the bottle.
In a high humidity area you can seal the plastic cap to the bottle with a piece of aluminum tape (the type used on ductwork). NO OIL WHATSOEVER to prevent rust, as it could cause an explosion!!

You should weigh the bottles, mark the weight on them. Re weigh them annually as many of them will leak out, albiet slowly. Obviously, those that are leaking should be used first.

I no longer store those little bottles. I had 6 of them and after about 6 months, 4 of them had leaked off empty. They were stored inside the house. I kept smelling propane and was constantly checking my lines for leaks. I'm glad I finally found the leak! Now I fill 10 gallon tanks, the kind used on camper trailers, and have an adapter to use with the small camping appliances. The adapter is available at WallyWorld for around $10.

I hope you have better luck with them than I did. A friend had the same problem.